Catheter ablation is a surgical procedure in which a catheter having an ablation tip is fed through various biological lumens to reach targeted tissue within the body. Radiofrequency current (“RF current”) is transmitted through electrodes disposed within the biological lumen and emitted from the ablation tip into the targeted tissue. The ablation tip is placed in close proximity to or in contact with the targeted tissue to maximize the amount of RF current supplied directly to the targeted tissue and limit the amount of untargeted tissue exposed to the RF current. Because the ablation catheter is navigated through existing biological lumen to reach the targeted tissue, catheter ablation surgery is less invasive than other available surgical techniques for reaching the targeted tissue, such as open heart surgery.
However, biological lumens and particularly blood vessels are often circuitous in nature and typically intersect many other biological lumens, presenting challenges with respect to catheter navigation therethrough. In order to reach the targeted tissue, the ablation tip must be threaded through the bends in the biological lumen and through the various intersections to reach the targeted tissue. Once near the target tissue, the operator must be able to accurately position the tip of the catheter for adequate delivery of the ablation energy. The difficult navigation process required can extend the surgical time considerably and can result in injury to the patient.
Catheter bodies often comprise an internal pull wire for deflecting the tip of the catheter body to more easily navigate the various turns and bends of the biological lumen. The pull wire is typically affixed proximate the tip of the catheter body and extends through the catheter body exiting the end of the catheter body that remains outside the patient's body. An operator can apply a pulling force to the pull wire to cause the tip of the catheter to deflect. Handles are often affixed to the proximal end of the catheter body to manipulate the pull wire for control of the defection of the catheter. However, different operators often have different tactile preferences as to the amount of force required to deflect the tip of the catheter a given amount. A standardized or factory set force-to-deflection relationship may cause some operators to over-deflect the catheter tip (thus denying the operator resolution in deflecting the tip), while causing others discomfort because the force requirement for a given tip deflection is uncomfortably high.
One steering mechanism used for deflection of a catheter tip is the so-called “steering spine.” Steering spines are characterized by a continuous portion (i.e. the “spine”) that extends from the proximal to the distal end of the steering mechanism. An advantage of the steering spine is that the resilience or elasticity of the continuous spine portion generates its own restorative force when the spine is deflected from its at-rest position, thus negating the need for a second pull wire to restore the tip to a straightened geometry. However, the deflection steering spines implementing a single pull wire are “unidirectional”—i.e., can only deflect in one direction relative to the steering spine (typically away from the steering spine). Thus, deflecting the catheter tip in a direction opposite an instant orientation of the steering spine (i.e., in the direction towards the instant orientation of the steering spine) requires first rotating the entire catheter assembly 180° about its longitudinal axis.
Other catheters utilize steering systems that are “bi-directional,” i.e., capable of deflecting in two directions. These systems typically implement two pull wires. Often, the tip deflection mechanism does not include a steering spine, so there is no passive or elastic restorative force. Instead, some bi-directional steering systems rely on the pulling action of the second pull wire to actively restore or reverse the action of the first pull wire, and vice-versa.
Certain catheter handles include tactile feedback mechanisms, such as vibrators, to inform the user when a certain condition has been met. An example of such tactile feedback mechanisms are disclosed in U.S. Patent Application Publication No. 2011/0251554 to Romoscanu, assigned to the owner of the present patent application and the disclosure of which is incorporated by reference herein except for the claims and express definitions contained therein.
A device that can accommodate the tactile preferences of an individual operator in the control of catheter tip deflection would be welcome. A frictional device that can substantially match the varying restorative force of the steering spine across the range of tip deflection while reducing the force requirements at low tip deflections would also be welcome. A catheter system that implements non-auditory sensory perceptions would also find utility in the modern operating MOM.